Mosquito-borne diseases continue to increase in significance as pathogens of humans and animals. Many of these diseases remain intractable to control or resurgent in many areas of the world. Novel control strategies are desperately needed for control of these important diseases. The overall goal of this research is to develop novel control strategies that target the vector or vector-pathogen interface to interrupt the cycle of transmission of vector-borne pathogens. New information concerning vector-pathogen interactions and vector molecular biology will be derived using virus transduction and expression systems, and this new information may be exploited to control vector-borne diseases. Sindbis (Alphavirus, AV) and Aedes densonucleosis (DNV)-based virus transduction systems have been developed for Aedes aegypti mosquitoes. AV and DNV expression systems will also be developed for expression and knock out of genes in Anopheles gambiae. These systems will be used to characterize biologically genes of interest (GOIs) in vivo in the medically important vectors. Genes and gene products identified as determinants of malaria and filaria transmission in Projects 1 and 2 of this TDRU proposal and by others will be characterized in vivo in Aedes and Anopheles vectors. The DNV systems possess biocontrol potential in addition to transduction capability of GOls. Densoviruses are extremely stable in the environment and are target specific. The potential for DNV systems to infect and to transduce genes that alter vector competence or vectorial capacity will be determined. Genes to be investigated include insect- specific toxin, juvenile hormone esterase, and Aedes headpeptide I, which regulates host seeking behavior. Transduction of such effector molecules into vector populations could provide novel control mechanisms for vector-borne diseases.